A large proportion (some estimates are as high as 25%) of the electricity generated in the United States each year goes to lighting. Accordingly, there is an ongoing need to provide lighting that is more energy-efficient. It is well-known that incandescent light bulbs are very energy-inefficient light sources. About 90% of the electricity they consume is released as heat rather than light. Fluorescent light bulbs are more efficient than incandescent light bulbs (e.g., by a factor of about 10) but are still less efficient as compared to solid state light emitters, such as light emitting diodes (LEDs).
It will be appreciated that embedding LEDs and associated electrical circuitry for selectively turning such embedded LEDs on and off within the structure of a laminated pair of curved or non-curved glass plates, and using the same as a part of the safe visible viewing scheme for drivers and their passengers, would offer many potential advantages for motor vehicle manufacturers. For example, such techniques could provide increased interior space compared to, for example, alternative lights that are exterior to the glass but attached to the glass. Such assemblies also could have a lower overall weight, e.g., as the housing for a light that is external to the glass but attached to the glass or separately mounted as an assembly to the body, could be eliminated. The reduction of the components, and the ability to use lower cost components, could reduce manufacturing/assembly related costs. LEDs also sometimes offer improved reliability for the overall light assembly compared to, for example, an incandescent light bulb inclusive assembly external to the glass but attached to the glass (e.g., given the delicacy of the lamp filament compared to the solid state LED).
Unfortunately, however, there are several disadvantages or difficulties in implementing such systems. One category of disadvantages/difficulties relates to the geometric linking of the glass orientation and the axis of the light emitting pattern. For example, the optical axis of the light output typically will be geometrically normal to the surface of the glass, when it instead would oftentimes be desirable for the optical axis of light output to have a different orientation. More particularly, because the surface where the LEDs will be located typically will be angled and/or curved, light may be output and/or spread in undesired directions.
An example of the potential problem with embedded LEDs is in their use as Center High Mount Stop Lamps (CHMSLs); tail lights for cars, trucks, and other vehicles; etc. Those lamps typically are in housings that oftentimes are plastic and attached to the interior surface of the backlite of a vehicle, or affixed otherwise to the body. Federal regulations in the United States stipulate the intensity, color, physical size, orientation, and operation of the lamps. More particularly, the light output optical axis should be oriented largely in the direction of the driver of a vehicle behind the stated vehicle. If the back light is oriented at right angles to the front-to-back axis of the vehicle, then the CHMSL light axis will be substantially in alignment with the axis of the vehicle and, thus, the lights will shine back on the driver of the trailing vehicle. However, if the backlite is declined at an angle, then the lights will shine “up” relative to the direction of the driver in the trailing car. In fact, there are as many angles of declination, as there are models of vehicles.
FIG. 1, which plots the spatial distribution of a typical lensless LED, shows the output of a typical LED such as might be used in a typical CHMSL. The figure shows the light output in relative percent as a function of angle away from its local normal. This pattern is generally symmetric and can be represented as a “cosine” distribution, for example. It can be seen that, in this example, for small deviations from the “0” angle (which corresponds to normal to the LED surface), the light output percent relative to the 0 angle is only a few percent less than along the normal. That is, the light is nearly as bright a few degrees away from the normal. Yet at an angle of, for example, 40 degrees away from normal, the light output has fallen to less than 80% of the normal output. This essentially means that if the normal output is the level of light output that is desirable in the direction of the viewer, 20% brighter LEDs should be included to compensate for this drop-off.
This increased brightness requirement may, however, impact the temperature that the embedded LEDs will rise to during operation. Higher LED temperatures are known to reduce both the LED output brightness, as well as the lifetime of the LEDs. And even if the brightness of the LEDs could be increased to compensate for the loss in brightness off-axis, the on-axis brightness might be high enough to be a distraction.
Thus, it will be appreciated that there is a need in the art for techniques for altering the axis of light output from embedded LEDs relative to the geometric surface of the glass. For example, it will be appreciated that there is a need in the art for techniques for making the axis of the light produced by embedded LEDs coincide with the front-to-rear axis of a vehicle, while still allowing for different angles of the back light of different vehicles.
One aspect of certain example embodiments relates to optically altering the axis of light output from embedded LEDs relative to the geometric surface of the glass on which they are mounted.
In certain example embodiments of this invention, a window for a vehicle is provided. First and second glass substrates are laminated to one another via a first laminating material. A sheet supports a plurality of LEDs. An optical element is interposed between the LEDs and an intended viewer of the LEDs. The optical element is structured to redirect light output from the LEDs in a direction that is substantially in alignment with a major axis of the vehicle.
According to certain example embodiments, the LEDs and the optical element are disposed between the first and second glass substrates; and/or the optical element and the LEDs are disposed between the cover substrate and the first substrate, and the optical element and the LEDs are laminated to the cover substrate and the first substrate via a second laminating material.
According to certain example embodiments, the plurality of LEDs are provided as a part of a CHMSL, the CHMSL being controllable by a controller remote from the LEDs.
In certain example embodiments of this invention, an electronic device is provided. First and second glass substrates are laminated to one another via a first laminating material. The first and second substrates have substantially matching curvatures and/or are adapted for installation at an angle that is not normal to a first intended viewer's line of sight. A sheet supports a first set of LEDs. A first holographic or ruled optical element is interposed between the first set of LEDs and the first intended viewer of the first set of LEDs. The first optical element is structured to redirect at least some light output from the first set of LEDs such that a substantial amount of light output from the first set of LEDs is focused in a first direction that is generally normal to the first intended viewer's line of sight. The first set of LEDs and the first optical element are (a) disposed between the first and second glass substrates, and/or (b) laminated between a cover glass substrate and the first substrate with a second laminating material.
According to certain example embodiments, a second set of LEDs and a second holographic or ruled optical element are provided, with the second optical element being interposed between the second set of LEDs and a second intended viewer, and with the second optical element being structured to redirect at least some light output from the second set of LEDs such that a substantial amount of light output from the second set of LEDs is focused in a second direction, different from the first direction, that is generally normal to the second intended viewer's line of sight.
Corresponding methods also are provided in certain example embodiments. For instance, in certain example embodiments of this invention, a method of making a window for a vehicle is provided. First and second glass substrates are laminated together with a first laminating material. A sheet supporting a plurality of LEDs and an optical element to be oriented between the LEDs and an intended viewer of the LEDs are provided. The optical element is structured to redirect light output from the LEDs in a direction that is substantially in alignment with a major axis of the vehicle. The LEDs and the optical element are laminated (a) between the first and second glass substrates, and/or (b) between a cover substrate and the first substrate in connection with a second laminating material.
These sorts of electronic devices may be used in sign, display, logo illumination, tail light, CHMSL, and/or other applications.
The features, aspects, advantages, and example embodiments described herein may be combined in any suitable combination or sub-combination to realize yet further embodiments.